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Auto-ignition characteristics of end-gas in a rapid compression machine under super-knock conditions

Qi, Yunliang and Wang, Yingdi and Li, Yanfei and Wang, Jianxin and He, Xin and Wang, Zhi (2019) Auto-ignition characteristics of end-gas in a rapid compression machine under super-knock conditions. Combustion and Flame, 205 . pp. 378-388. ISSN 0010-2180.

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Spark ignition induced super-knock was generated in a rapid compression machine using stoichiometric iso-octane/O_2/N_2 mixture. In addition to the pressure traces, the combustion processes were also recorded using high-speed photography, from which the characteristics of the end-gas auto-ignition were analyzed. The effect of negative temperature coefficient (NTC) on the end-gas auto-ignition was investigated using detailed and reduced reaction mechanisms. The end-gas auto-ignition of diluted methanol/O_2/Ar mixture without NTC behavior was also tested for comparison. The results showed that the end-gas auto-ignition of iso-octane/O_2/N_2 mixture exhibited a two-stage ignition process. During the second ignition stage of the end-gas, two auto-ignition events with very short time interval were sequentially observed in the end-gas region. The first auto-ignition event generated a weak shock wave, and the second one initiated detonation. Both the two auto-ignition events occurred near the wall but at different sites. Due to the heat loss to the wall, the near-wall region is generally considered to be colder than the adiabatic core region, and thus the near-wall auto-ignition of end-gas was usually considered as a result of fuel's NTC behavior. However, in this study the chemical kinetic calculation showed that the evolution of the end-gas almost bypassed the NTC region in the ignition delay-temperature diagram. Furthermore, for the methanol/O_2/Ar mixture the end-gas auto-ignition also started at the very near-wall region. Considering that methanol fuel does not has an NTC behavior, the near-wall auto-ignition of methanol/O_2/Ar mixture should be a result of other factors than NTC. Therefore, it was concluded that NTC might not play a dominant role in the near-wall auto-ignition of the end-gas.

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Additional Information:© 2019 The Combustion Institute. Published by Elsevier Inc. Received 18 January 2018, Revised 5 July 2018, Accepted 7 April 2019, Available online 3 May 2019. This work was supported by National Natural Science Foundation of China (Grant nos. 91541206, 51706121 and 21761142012); and China Postdoctoral Science Foundation (Grant no. 2017T100076).
Funding AgencyGrant Number
National Natural Science Foundation of China91541206
National Natural Science Foundation of China51706121
National Natural Science Foundation of China21761142012
China Postdoctoral Science Foundation2017T100076
Subject Keywords:Super-knock; End-gas auto-ignition; Detonation; Negative temperature coefficient; Rapid compression machine
Record Number:CaltechAUTHORS:20190503-124821579
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Official Citation:Yunliang Qi, Yingdi Wang, Yanfei Li, Jianxin Wang, Xin He, Zhi Wang, Auto-ignition characteristics of end-gas in a rapid compression machine under super-knock conditions, Combustion and Flame, Volume 205, 2019, Pages 378-388, ISSN 0010-2180, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95204
Deposited By: Tony Diaz
Deposited On:03 May 2019 20:07
Last Modified:03 Oct 2019 21:11

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